1. Field of the Invention
The present invention relates to a cooling device such as a refrigerator or freezer in the form of a cupboard or a chest with a cooling space surrounded by a wall and a door.
2. Description of the Related Art
Cooling devices may include, for example, refrigerators, freezers, refrigerator-freezer combinations, and deep freezes. These types of cooling devices are typically manufactured on a large scale. Since these devices are mass produced, even slight simplifications with the manufacture and assembly may lead to high savings in costs. Most cooling devices are thermostat-controlled in that they are switched on and off according to the temperature of the refrigeration space. However, some newer cooling device also include an electronic rotational speed controller for controlling the motor which drives the compressor. These types of controllers such as, for example, frequency converters may be miniaturized and manufactured at acceptable costs. A cooling device having such a controller is disclosed, for example, in PCT/DK96/00300. In the cooling device disclosed by this reference, the compressor is designed as an essentially closed pot and the frequency converter is seated within a box attached laterally to this pot.
The arrangement of the frequency converter in a box attached laterally to a pot of the compressor is not desirable for many reasons. Many individual components are required to be cabled to the refrigerator controller which is complicated and thus expensive and prone to breakdown. Furthermore, the compressor pot is subjected to severe mechanical oscillations which are caused by the rotation of the motor and the oscillation of the piston which forms a complex mechanical oscillation formation. This is why the compressor pot is usually suspended using a soft suspension such as rubber mounts. The oscillations exerted onto the sensitive frequency converter electronics may cause fractures of the circuitboard, contact weaknesses, or other disturbances created by mechanical oscillations. When a repair is required, both the compressor pot and the frequency converter are required to be exchanged since these are designed as a unit. Since these components make up a large part of the total price of the cooling device, it would be desirable to be able to exchange these components individually. Furthermore the arrangement of the frequency converter on the compressor pot may subject the frequency converter to thermal energy which is also undesireable.
It is an object of the present invention to provide a cooling device with a drive motor of a compressor activated by an electronic rotational speed controller which overcomes the problems of the prior art. The cooling device is inexpensive to manufacture, functions reliably and is repair-friendly.
The object is achieved by a cooling device having a cooling space wall and a door defining a cooling space, a compressor having an electrical drive motor, a rotational speed controller operatively connected for controlling the electrical drive motor, a cooling medium circuit having a condenser, an evaporator and an expansion means arranged between the condenser and the evaporator, a temperature control for controlling the temperature of cooling space temperature, and a constructional unit in which both the rotational speed controller and the temperature control are arranged. The constructional unit is arranged so that said constructional unit is spacially separated from the compressor.
The present invention groups the rotational speed controller together with the temperature control in one constructional unit to provide a unit which is exchangeable separately from the compressor. Furthermore, the constructional unit is designed to be exchanged quickly and simply during a repair. This constructional unit formed of at least the temperature control and rotational speed controller forms a central connection component of the cooling device. The main power supply for the cooling device is connected to this constructional unit. The output of the rotational speed controller is connected to the compressor via a connection cable. Further cable connections are made as required by the arrangement and scope of the constructional unit.
The constructional unit may be arranged on the compressor. In that case, the constructional unit may be attached on the compressor housing via an oscillation-damped connection. However, the constructional unit comprising the rotational speed controller and at least a temperature control is preferably arranged spacially separated from the compressor. Such an arrangement has the considerable advantage that the sensitive electronics of the constructional unit may be arranged where it is favorable with regard to the oscillation loading and heat removal. Furthermore, all of the electronics of the cooling device are grouped together in a constructional unit. Apart from the rotational speed controller and the temperature control, further electrical or electronic components may also be arranged in the constructional unit when appropriate. When the electronics are arranged so that they are spacially separated from the compressor or at least in an oscillation-insulated and/or thermally-insulated from the compressor, the long-term behavior improves which leads to an improved operational dependability of the whole cooling device. Furthermore, the compressor and electronics may be exchanged separately during repairs. The separate exchangeability of the compressor and electronics is important because exchanging the compressor requires that the coolant circuit be opened which entails complicated mechanical interventions in the system. In contrast, the exchange of the electronics requires only a release of a screw or snap connections and the electrical contacts. Accordingly, the removal to the electronics may be carried out by less qualified personnel, i.e., knowledge of the coolant circuit is not required. Finally, the constructional unit may be arranged with as many further components as possible so that the number of components to be assembled in the cooling device may be further reduced. The further components may, for example, include lighting, temperature display, operating condition display, temperature sensor. Where appropriate, these further components are integrated into the constructional unit.
The constructional unit may also include a sensor for acquiring a reference variable for the cooling space temperature control, specifically for the control. Such a sensor may in its simplest form be a temperature sensor. However, the temperature may also be acquired indirectly via dampness or other suitable sensors. If such a temperature sensor is provided in the constructional unit, the conducting path for the signal to the control electronics is short. The sensor according to the arrangement of the constructional unit may be arranged within the constructional unit so that the sensor projects through a recess in a wall of the cooling device into the space to be cooled while the remaining part of the constructional unit is arranged outside. However, the sensor may also be arranged on the outer side of the wall and connected to this in a heat-conducting manner, so that a penetration through of the cooling space wall may be spared. This in turn brings advantages with respect to the heat insulation of the cooling space as well as the demands on the seal of the constructional unit.
For the arrangement of the constructional unit within the cooling device, there are many possibilities from which to select depending on the constructional size of the refrigerator, on the waste heat to be removed in the power electronics, and on other demands on the design. The constructional unit may be seated within the cooling space or outside. If it is seated outside it may bear on the walling limiting the cooling space or may be arranged at a distance to this. The latter arrangement is favorable when the waste heat of the power electronics which are arranged within the constructional unit is to be dissipated away completely to the surrounding air and not indirectly or directly via the cooling medium. At the same time the constructional unit may be arranged in the air-side convection flow of the condenser. The constructional unit is preferably arranged below the condenser since the air is at its coldest. If a removal of the waste heat is to be provided via the cooling medium then it is useful to arrange the constructional unit either within the cooling space or directly bordering on the wall defining the cooling space or at least connected in a heat-conducting manner to the wall. In arrangements in which the operating parts are included as a part of the constructional unit, the constructional unit is to be arranged such that the operating parts are accessible to the user.
The rotational speed controller may include a frequency converter. However, the speed controller may also be formed as a phase control or even as a pulse cascade circuit. With the latter, the electronics include a switch and control which controls the switch.
If the constructional unit is arranged within the cooling space or directly bordering the door or lid, then the door or lid switch contact for the cooling space lighting may be integrated in the constructional unit and where appropriate also the lighting itself. Furthermore with an arrangement of the constructional unit within the cooling space it may be useful to co-integrate into the constructional unit a fan for circulating the air located in the cooling space. The air circulation improves the waste heat removal and also creates a largely uniform temperature distribution within the whole cooling space.
If a transmitting and/or receiver device for wireless data transmission of the device is to be provided, then this is usually integrated into the constructional unit. Accordingly, all the electronics of the cooling device are grouped together in the constructional unit which brings with it advantages with respect to manufacturing technology. The wireless data transmission function may, for example, allow the setting of the cooling space temperature from the outside or for incorporating the device into a computer-controlled system. The provision of a remote control may be used when the arrangement of the constructional unit is such that a direct access for setting purposes is not possible or is difficult.
When the cooling device comprises a freezing apparatus in which the cooling space temperature is designed to be significantly below 0xc2x0 C., a defrosting at least of the evaporator is required at periodic intervals. The defrosting may be effected largely or completely automatically by way of a suitable defrosting control. The defrosting control may be integrated in the constructional unit. It may be useful to integrate the constructional unit into the door or flap of the cooling device since then it is easily accessible and there may also be co-integrated further switches and displays.
The cooling of the power electronics by the cooling medium itself or via the air located in the cooling space, although being effective and permitting a high degree of miniaturization of the power electronics, worsens the total efficiency of the device. Thus alternatively to this, the constructional unit may be arranged near or on the outer side of the device so that the waste heat of the power electronics is removed via the surrounding air. According to the spacial conditions it may also be useful to provide a convection cooling to the outside as well as also a cooling via the cooling medium or the cooling space.
High quality refrigerator-freezer combinations are usually provided with two compressors. These devices also include two electronic rotational speed controllers and temperature controls. These rotational speed controllers and temperature controls may be unified in a common constructional unit.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.